How to know if your PC has malware
Updated August 2026 • By MK Janway, SilverLink LLC
Malware isn't always obvious. Here are the most common warning signs, a quick DIY checklist, and when to call a pro.
8 Warning Signs of Malware
- 1
Slow Performance
Your PC takes forever to boot, apps lag, and everything feels sluggish even after a restart.
- 2
Pop-Up Ads Galore
Ads appear out of nowhere, even when you're not browsing. Adware is often the culprit.
- 3
Strange Toolbars or Extensions
New browser toolbars appear that you didn't install. Homepage changes without your permission.
- 4
Programs Opening Automatically
Apps you didn't open launch by themselves. Files appear on your desktop out of nowhere.
- 5
Security Software Disabled
Your antivirus suddenly turns off and won't turn back on. This is a major red flag.
- 6
Slow Internet
Internet feels sluggish even after a router reboot. Some malware uses your bandwidth.
- 7
Missing or Corrupted Files
Files won't open, or you get "access denied" errors on files you've always used.
- 8
Unusual Activity on Your Accounts
Friends get strange emails from you, or you see unauthorized logins on your accounts.
Quick DIY Checklist
- Run a full scan with Windows Defender or your antivirus
- Check Task Manager for unknown processes (Ctrl+Shift+Esc)
- Review browser extensions and remove anything unfamiliar
- Change passwords on email, banking, and social media
- Enable two-factor authentication wherever possible
- Back up important files to an external drive or cloud
When to Call a Pro
DIY steps can help, but they're not always enough. If you're still seeing symptoms after running scans, or if you're worried about sensitive data, it's time to call someone who knows what they're doing.
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